Car's slow, wtf??
 

Hey guys, I gotta have some help with this car. It's driving me crazy now and I got to know what the deal is.

You see, it's lost a step. I don't really know why, but it's a lot slower then it used to be. It used to run pretty decent, I could go mid 15s easy even in the summer n/a. I would get 15.5, 15.6 all the time. Now it's in the 16s, like a 16.3, 16.4. Nothing's changed. And it even seems to run ok, no cutting out or anything. It's like it just suddenly quit making the horsepower it used to.

The one problem is this, it has a check engine light on for egr and rear o2 sensor. Could those cause this big of a

difference? But no noticable effect on the way the car runs? Like I say, it runs, idles, drives just fine, just goes almost

a second slower in the quarter mile. It's a high milage car too I might add but with a swapped out used motor. And both motors have ran the 16s on me so that makes me think it's not the motors fault here.

Any ideas?

replace the sensor....

With your rear 02 sensor, the engine is in safe mode which it retarts the timing which gives you less power. Replacing that and getting the system back into normal mode with some premium gas should get you back in to the mid 15's.

I am having the same problem with my rear 02 sensor, but my maxima is just for daily beater and my fordlightning is my weekend car so its not a biggie.

02 sensors aren't cheap either.

I thought the rear sensor didn't matter much, at least it seems like I read that on here somewhere. I have no cats, just a test pipe so I thought that would be the problem there.

You really think the rear sensor will also fix the egr code and make this thing run like it should? That would be awesome because I no less then nothing about egr stuff or how to fix it.

if u have egr problems check the stickies man.. i had a low flow code.. i cleaned the entire system and the car runs a lot better now .....

UUUMMM Point? It is a Maxima, no suprises.

It's that simple bro...

1) Fix the problems. Replace the O2 and get the EGR system working correctly.
2) Tune up? Plugs, air filter, fuel filter.
3) Go back to the track and have fun.

You'd think I would I know this by now, but would one of the front O2 sensors cause the ECU to run in safe mode as well?

Not quite. A few points:

1. The rear o2 sensor isn't used for direct engine control.

2. The o2 sensor "safe" mode when the front o2's go bad results in running in open loop full-time, aka rich. Not pulled ignition timing.

3. Even IF the rear o2 was to blame and it was in "safe" mode open loop performance would be unaffected since the ECU ignores o2 sensor signals during this condition.

4. Ignition timing during open loop is determined by injector pulse width and RPM to determine load, not by o2 sensor readings.


As for the EGR system, it's not used at WOT anyway. Something else is going on.

So your saying basically I'd be wasting my money replacing sensors and/or egr stuff as far as track performance is conserned? That's all I really care about. I just don't want to get into a big money deal is all, I'll replace a sensor but that's about it.

You want your car to run tip top but don't want to replace sensors that are failing and stuff??? When you run a car hard you have to baby it with maintenance. No ways around it. It cost money to go fast.

Maybe you missed what i said in post # 10 or just don't understand it. The things he has codes for will NOT affect WOT performance.

Could be effecting his 60' launches though...

You're right, since open loop doesn't start until 3000 RPM or so. But you really think that could cause the car to be almost a full second slower?

Ha...now I know why my exhaust is black :p

Damn dude, that's totally spot on. The car does seem to turn it up a notch at 3k and the 60's are crap. Actually there only about .2 off normal and I don't quit see that causing nearly a second.


And as for the post about me not wanting to replace sensors and stuff, I said I WOULD replace an o2 sensor, I just don't want to start spending A LOT, cause I don't have a lot to spend right now. If it's going to cost me several hundred bucks I'll just have to drive it like it is for a while. And this is why I want to know for sure a sensor will fix it, cause if it doesn't, I wasted nearly a 100 bucks.






Is there any way to disable the egr stuff on these cars? Make it so it doesn't matter if it works or not, so it's kind of in this "open loop" all the time, where it doesn't use it? I know on some other cars you can ditch the egr and emissions systems. I'd be curious to know if that below 3000 is really killing me that bad or not. Or I could just get a 3000 stall and some slicks, heh.